This invention relates to a medical diagnostic method and, more particularly, to an in vitro diagnostic method for renal disease or nephritis in association with systemic lupus erythematosus.
Systemic lupus erythematosus (SLE) is a rheumatic disease; it is a chronic inflammatory disease that apparently results from an immunoregulatory disturbance caused by various factors. The lupus erythematosus cell is believed to result from an antinuclear antibody whereby SLE is characterized as an autoimmune systemic disease. The systemic nature of the disease is evident by various clinical manifestations, including renal involvement in SLE. The renal involvement is usually glomerular.
Various methods have been described heretofore for detecting renal disease in SLE. Thus, kidney biopsies have been widely used to determine renal involvement in SLE. Immunofluorescence is a principal technique used in identifying the immunopathogenesis of renal disease.
The presence of antinuclear antibodies (ANAs) is a diagnostic hallmark of SLE since ANAs appear in nearly all patients with SLE. The fluorescent-ANA test is one of the most widely used and accepted tests for the detection of circulatory ANAs.
Antibodies to DNA have been useful in specific tests in rheumatology. On the one hand, high-affinity antibodies reacting with double-stranded DNA (dsDNA) are virtually unique to patients with SLE and only rarely found in other conditions. On the other hand, low-affinity antibodies that react with denatured or single-stranded DNA (ssDNA) occur in a wide variety of other rheumatic diseases.